Dear All:
I apologize for asking such an elementary question, but I could not find an
adequate response on line. I am hoping to receive some help with the
interpretation of the Intercept coefficient in the gam model below.
I1 through I3 are dummy coded "Item difficulty" parameters in a data set that
includes 4 items. If the Intercept is the value of Y when all other terms are
0, am I correct in assuming that it also equals the difficulty of item 4 (dummy
coded 0 0 0 )?
Thank you for your help.
Lidia
Family: gaussian
Link function: identity
Formula:
Score ~ I1 + I2 + I3 + s(TimeI1, bs = "cr", k = 7) +
s(TimeI2, bs = "cr", k = 7) + s(TimeI3, bs = "cr", k = 7)
Parametric coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) 4.70968 0.09547 49.330 < 2e-16 ***
I1 -0.22188 0.21767 -1.019 0.308157
I2 0.51236 0.16592 3.088 0.002042 **
I3 -0.60697 0.18258 -3.324 0.000902 ***
---
Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
Approximate significance of smooth terms:
edf Ref.df F p-value
s(TimeI1) 3.820 3.820 4.587 0.001331 **
s(TimeI2) 2.491 2.491 6.271 0.000784 ***
s(TimeI3) 3.481 3.481 8.997 1.54e-06 ***
---
Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
R-sq.(adj) = 0.057 Scale est. = 2.131 n = 2079
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